The present technology relates to a solid-state imaging device and an electronic apparatus, and in particular relates to a solid-state imaging device with improved color reproducibility and an electronic apparatus including such a solid-state imaging device.
In the related art, solid-state imaging devices employed in digital still cameras and other electronic apparatus have color filters formed on photoelectric conversion regions to allow light of only a specific wavelength band to enter each pixel in the photoelectric conversion region. This allows the solid-state imaging device to obtain color information corresponding to the color of the color filter in each pixel in the photoelectric conversion region.
The color filters of different colors are arranged, for example, in a so-called Bayer array in which the primary color filters of three primary colors including red, blue, and green are arranged in a checkered pattern. In this arrangement, in some pixels, color information of colors other than the color arranged on these pixels is obtained by complementing the color from other pixels in their peripheries. Color information obtained by arithmetical operation complementing the color by other colors may differ from the original color information and may not correctly reproduce the actual color.
Japanese Unexamined Patent Application Publication No. 2003-303949, for example, proposes a solid-state imaging device having a structure outputting image signals, which are converted from incident light of different wavelength bands, from a single pixel without complementing colors from other pixels in its periphery.
Referring now to FIG. 1, an exemplary configuration of the solid-state imaging device capable of obtaining image signals of three colors from a single pixel will be described.
FIG. 1 shows a sectional view of a solid-state imaging device 11 including photoelectric conversion regions 13B, 13G, and 13R stacked within a silicon substrate 12 of each pixel. In the solid-state imaging device 11, a P-type well 14 is formed between these regions.
The photoelectric conversion region 13B photoelectrically converts and outputs signals corresponding to the intensity of light of blue wavelength band through a B signal output unit, the photoelectric conversion region 13G photoelectrically converts and outputs signals corresponding to the intensity of light of green wavelength band through a G signal output unit, and the photoelectric conversion region 13R photoelectrically converts and outputs signals corresponding to the intensity of light of red wavelength band through an R signal output unit.
FIG. 2 shows spectral sensitivity characteristics of the solid-state imaging device 11, i.e., relative sensitivities to the wavelengths of the blue output from the photoelectric conversion region 13B, green output from the photoelectric conversion region 13G, and red output from the photoelectric conversion region 13R.
The spectral characteristics in FIG. 2 show that the spectrum distributions of the blue, green, and red outputs are broad, indicating that the solid-state imaging device 11 has low performance of spectrum resolution.
More specifically, as shown in the spectral characteristics in FIG. 2, the spectrum distributions of the outputs (blue, green, and red outputs) from the stacked photoelectric conversion regions 13B, 13G, 13R significantly overlap each other. For example, looking at the relative sensitivities at a wavelength of 550 nm at which green should be output, the output from the photoelectric conversion region 13G formed in the intermediate layer of the three layers stacked in the depth direction of the substrate and the output from the photoelectric conversion region 13R formed in the deepest layer are substantially the same.
When incident light has a wavelength of 550 nm, which is originally green light, only green should be output. Red would be output, however, at the same intensity as green, which would make it difficult to reproduce the original color because an intermediate color between green and red, i.e., orange, would be reproduced if the color information that should be of green is reproduced on the screen without being separated from red. Due to these spectral characteristics, complicate signal processing would be necessary to reproduce the original color; change in color temperature of the incident light would make it difficult to reproduce the color correctly.